As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ACFT WAS NOT GROUNDED BECAUSE OF THIS SDR REPORTABLE EVENT. DEFECT WAS IDENTIFIED DURING RON MAINTENANCE; IT DIDN'T CAUSE A FLIGHT DELAY. REFERENCE LP549403 ITEM #1. DURING HEAVY CHECK EPSU BATTERY 11WL FAILED EPSU TEST, PTT FLAG BATTERY FAULT. REF AMM 33-51-38-000-002-1A & 33-51-38-100-002-A REPLACED EPSU 11WL. OPS TEST GOOD.